Hi Dave, On Fri, 2024-08-16 at 11:17 -0400, Dave Vasilevsky wrote: > > Could you verify that this change actually fixes the problem? This would > > save me some work. > > Verified with PPC qemu. I fail to boot with "You can’t boot a kdump kernel > from OF" with > CONFIG_CRASH_DUMP on, and I boot fine with it disabled.
Thanks for the confirmation. > Details: > * Tested against the Debian 6.10.4-1 kernel as unpacked with `dget > https://deb.debian.org/debian/pool/main/l/linux/linux_6.10.4-1.dsc` > * Built with the GCC 14.2.0 powerpc toolchain from kernel.org > * Using the exact kernel config from a stock sid powerpc system: > https://gist.github.com/vasi/be13936e9de9b5a6db8a71897c731aef. Tested > building both without any change, and with the change to CONFIG_CRASH_DUMP. > * Built with `PATH=... ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- make > bindeb-pkg` > * Tested with a Debian sid powerpc VM in qemu 6.2. > > Do you need me to try this kernel against real hardware? I can dig an old > iBook out of the closet to see if it works. No, that should not be necessary. Thanks for the testing. > In terms of where this is coming from, I did some investigation: > * The value of CONFIG_CRASH_DUMP does change from n to y between 6.1 and > 6.10. So it is indeed > a problem with the config, not the kernel crashing under the same config as > before. > * The value of CONFIG_PROC_VMCORE also changes between 6.1 and 6.10, and it > depends on CRASH_DUMP. > But PROC_VMCORE seems to be enabled in Debian for years, so it's not > immediately obvious why > it's not in my config: > https://salsa.debian.org/kernel-team/linux/-/commit/432666d44950ff603d69537f5ea7c5843fac04d8 > * Looking at upstream, CRASH_DUMP changed to `default y` in 6.9! There's our > problem: > > https://github.com/torvalds/linux/commit/75bc255a7444801d64c7a7bd09e3f452f86b3585 > > * Easiest would be to simply change this downstream in Debian, since Open > Firmware is by far > the most common way of starting Debian powerpc. I don't know whether > upstream should change > or not--is there any real constituency that runs PPC Linux without OF, and > is also interested > in crash dumps? Maybe some embedded folks? Thanks a lot for investigating the cause of this and the testing, of course. You saved me a lot of investigating and debugging myself! > Up to you whether you'd like us to try to change this upstream as well, I'm > happy to chip in if so. Feel free to report this on the Linux PowerPC upstream kernel mailing list. It might be a good idea to add a conflict for CONFIG_CRASH_DUMP upstream when the 32-bit Power Macintosh option is selected. Adrian -- .''`. John Paul Adrian Glaubitz : :' : Debian Developer `. `' Physicist `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
